Matic electric inc



8 Sheets-Sheet l J. WICKS AUTOMATIC TELEPHONE SYSTEM Orlxzlnal Flled Dec 14, 1923 April 24, 1928.

April 24, 1928.

J. WICKS AUTOMATIC TELEPHONE SYSTEM Aprl 24, 1928. v 1,667,405

J. wlcKs AUTOMATIC TELEPHONE SYSTEM Original FiledDec. 14, 1923 8 Sheets-Sheet 3 Apl'i124, 1928. i 1,667,405

J. WlcKs AUTOMATIC TELEPHONE SYSTEM Original Filed Dec. 14. 1923 8 SheetS-Sheet 4 April 24, 192s. 1,667,405

J. WICKS AUTOMATIC TELEPHONE SYSTEM Original Filed Dec. 14. 1923 8 Sheets-Sheet 5 21T afimra's Pas/770A.

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April 24, 192s.

J. WICKS AUTOMATIC TELEPHONE SQE'STEM original Filed nec. 14,"1923 8 Sheets-Shen 6 all' Inman Dr- Jhn Maks W M? Ln- Q) l fmf April 24, 1928.

J. WICKS AUTOMATIC TELEPHONE SYSTEM Original Filed Dec. 14, 1923 8 Sheets-Sheet 7 m www .03 8. du. .Mw m 6: v 1 .Tu e e h S 8 m M3 T E2 /v wg vw w.|- ,5 .K SN. M Kmw m mmv E L 0 wEd Te .n Nq JEF w T1 M Aa C mm f wm A.r u o m om 2 .m Il E M H 7- r. m. F

Patented Apr. 24, 1928.

UNTTED- NSTATES 1,667,405 PATENT oFFlcsk JOHN woxs," or osx PARE; ILLINOIS, AssIGNoE,'EY MEsNE ASSIGNMENTsTo AUTO- MATIC ELECTRIC TNC., or CHICAGQILLINOTS, A CoEronA'rIoN or DELAWARE...

AUTOMATIC TELEPHONE SYSTEM. i

Applieationl'ed December 14, 1,923, Serial Ilio.` 680,596. Renewed August 26, 1927.

1. The present invention relates to automatic telephone systems in generahbutis concerned more particularly with automatic telephone systems in which talking battery is supplied from `a trunking switch (se lector) rather thanfrom a final switch (conare automatic and some are manual.

nector); and one, object is `the, production of new and improved circuit arrangements whereby the 1nter-ofiice trunk circuits in` a multi-office system embodying the invention are accurately balanced to prevent cross-tall: and other undesirable inductive defects, and are also grounded at one end only, so as to avoid the possibility of disturbances due t0 s varying ground potentials.

Another object of the present invention is to provide circuit arrangements whereby an automatic .telephone system of the above mentioned type may be interconnected with an existing manual telephone system,` and also 'to provide circuit arrangements such that the requirements of both systems may be met when calls are being extended from automatic subscribers'to manual subscribers, and` vice versa. Another Objectis to simplify as much as possible, consistent .with good operation, the circuits of the intermediate selectors and of the connectors.

There are a great manyy other objects and features of the invention which are more or less incidental to the objects set forth above and which will be brought out clearlyhereinafter. l L

Although various features of the invention are applicable `equally well to single oiiice automatic `telephone systems and to inulti-ofiice automatic telephone systems em# bracing any number of separate offices, it has been chosen to illustrate the present invention `in connection with a large multi-ofiice telephone system in which some of the ofices t is assumed further that the oices are laid out iii-districts with not more than ten offices per district and not more than ten districts. Accordingly, the first numerical switch, which in this case is a first selector repeater, is operated to select a trunk line extending to an office selector (in this case an incoming selector repeater) inthe desired district and this office selector responds to the second digit dialled to select the desired office. I 'L Referring now to the accompanying drawings comprising Figs. 140, inclusive,

Figs. 1-.9, inclusive, are circuit drawingsaiid show diagrammatically a sufficient amount of apparatus in a telephone` systemeinbodying the principles of the invention to enablethe invention to be understoochand Fig. l0 is a drawing layout showing how the sheets V of drawings should, be placed-together. A i

lFigs.` l-l, amount of equipment for a complete `connection between the line ofA substationA, Fig. l, in one office and the line of substation A, Fig. 4, in another oiiice. This connection is established automatically without the aid of an operator.

Figs. 5 and 6, when taken inconnection with the remaining part ofthe drawings, show va sufficient amount of equipment for making connections between the manual subscriberat substation AZand any automatic subscriber. c

Fig. 7 shows a so-called zero perators `cord circuit which may be taken into-use when the digit. O is dialled by any subscriber or by any A operator who is having difficulty in obtaining the desired connection The zero operator may extend the. connection either manually or automatically as lshc sees fit. 1

Fig.`8 shows `a toll recordingf'operators key circuit by means of which she answers calls extended to her position.` i y. l v

Fig. 9 shows a ,B. operators cord circuit by means `of which she completes connections to manual subscribers, such `as theone at A, when the trunk associated with the cord circuit is seizedl by an automatic `switch under the control of an automi-tic` subscriber or a calling operator who desires to extend a connection to a manual line.

The line switch C, Fig. `l, is mechanically of the well known rotary type in which the wipers have no normal position and are moved in a forward direction only. This line switch is employed for the purposeof connecting the associated line, .when calling, with an idle iirst selector. i

The first selector repeater D, Fig. l, which in this case functions as a district selector, is mechanically of thewellknown vertical and rotary type of switch, having its bank contacts arranged yin Ahorizontal rowsor levels. This selector is `arranged to supply talking battery to the calling subscriber and to repeat the interruptions producedfby the inclusive, Ishow suiiicient i callingisubscribei"s calling ldevice after it has selected an idle trunk. This `switch is also arranged to feed battery forward in the directioni ot the called` subscriber when 4the switchover7 operation occurs after the last digit in the number has been dialled.

The incomingselector repeater -E,,Fig 2,

which functionsv as an ohice selector, is mcchanicallyidentical with the first selector repeater D, Fig. 1,. lts circuits, however, diler somewhat 'from those of the latter switch, owing to the diii'erent requirements which the former meets, as will hereinafter appear The selector-.D,Fig. 6, is also anincoming selector repeater andr is identical with the incoming selector repeater E, Fig. 2. 'lhe selector D', however, functions as a district selector `like the irst selector repeater D, Fig. 1, and not as an oiiice selector.

n*The thousands selector' l?, llig. 3, is identical mechanically with `the switches mentioned above, but is somewhat simpler from thecircuit standpoint, owing to the fact that it has no repeating actions to perform. The hundredsselector G is identical with the selectorF.

The connector H is mechanically a vertical and rotary switch similar `to the selectors,

` but kits `circuits arearranged so that the shaft is operated in both its movements under the directive control of the calling subscriber. This connector responds to the interruptions produced` in the circuit olf its line relay .until it is completely operated, after which thel incoming trunk conductors are'extended straight through to the wipers and the line relay is cut oli'.

The various operator y circuits shown in thedrawings vare :more or less modifications of existingcircuits, having the new features to be explained ullyfhereina'fter.

lThe systemhavingbeen :described gener ally, the idetailed operation or the apparatus shown will now be given. For this purpose it will be .assumed that the subscriber at the automatic substation A, Fig. 1, desires to converse with the subscriber at the automatic substation A', Fig. 4t.

lVhen the subscriber atsubstation A removes his receiver, line yrelay `6 ot the line switch C energizes overline .conductors 2 and 3 and places ground on private normal conductor 4 at armature 12,.thereby making thecalled` line busy in thebanlrs of the con nectors having access to it and closing a circuit `for `switching relay and stepping magnet 7 in series. Line relay 6 alenconnects `testwiper 16 to the junction ot the windingsof switching` relay 5 and stepping magneti 7 at armature 13. Incase the trunk upon whiclrthe'wipers 1447, inclusive, ot the line switch are standing is idle,tthis latter operation is or norutility and switching relay/5` energizes immediately, seizing `5 is short circuited by the ground potential encountered on the busy test contact by test wiper 16 and does not energize. This same ground potential encountered by test wiper` 16 causes the energization of stepping magnet 7, and thewipers ot' the line switch are advanced step by step in search ot anvidle trunk owing to the buzzer-like action of stepping magnet 7, which interrupts its own circuit.A

, When an idle `trunk 'is reached, which trunk, it will be assumed, is the one comprising conductors 18-21, inclusive, switching relay `5 is no longer short circuited and energizes in series with stepping magnet 7. Stepping magnet A7, however, does not cnergize atthistime on account ot the high resistance of switching relay 5. Upon energizing, switching relay f5 opens `a point in the test circuitand prepares `the holding circuit at armature 10; connectsithe magnet of the meterli/l through wiper to the meter operating conductor 19 lat armature 9; and at armatures 8 and 11 disconnects line conductors@I and Strom the winding of line relay 6 and ground, respectively, ,and extends them byway of ywipers la and 17 and conductors 18 and 21, to the windings otlinerelayl ofrthe selector repeaterll Line relay 31, upon energizing, closes a circuit for release relay-32 at `armature 52. Release relayi32, upon energizing, opens a point in the circuit oi: release magnet fill and `prepares a circuit for vertical magnet 13 at armature 54, and at armature 58 it places ground on Irelease trunk conductor 20, .thereby completing the usual holding circuit `for switching relay of the line switch C-before the slow :acting `line relay 6 has had time to deenergize.

As a `further result of the energization ot line relay 31,it completes lat armature 5l a circuit for relay `37v as follows: from ground by way of the normally closed contacts controllediby armature 77' oi' relay 39, the upper winding-of relay 87, resting Contact and armature 64, working contact and armature 51, normally closed contacts controlled 4by armature 72, and resistance i6 to battery.

Relay? thereupon energica@ over this circuit and completes` at armature 68 a circuit for relay 38 whichincludes armature 67 et relay 36 and its resting contact. Responsive to the closure of this circuit, relay 38 energizes and opens at armature .70 a point in the circuit of switch-over relay 35, so :is to prevent the energization of switch-over relay until .the proper time occurs.

As a further rcsultof the energization oi the release relay 32, it places the dial tone ou the lower heavy talking conductor ture This dialtone is transmitted. to the CJi now proceed to set up the connection. Ac-

cordingly, he manipulates his calling device in accordance with `the irstdigit 1 in the desired number. When this occurs, line relay 31 deenergizes once momentarily and closes a circuit for vertical magnet 43 as follows: fromground by way of armature 52 and its resting contact, armature 54 and its working contact, armature 75 and its resting coutact, and vertical magnet 43 to'battery. By

the operationot'` vertical magnet 43, the

` wipers 79-81, inclusive, are raised opposite theirst level ot' bank contacts. The slow acting relay 33 isenergized in multiple with Vertical magnet 43 and at armature 56 closes f a point in the circuit ot steppingrelay 34, which is completed at ofi' normal contacts 45 as follows: from ground by way ot the work ing contact and armature 53, armature 62 and` its resting contact. working Contact and armature 56, armature 76 and its resting contact, off normal contacts 45, and stepping relay34to battery. Stepping relay 34, upon energizing, prepares a circuit for rotary magnet 41 at armature 58, and at armature 57 closes a lockingcircuit for itself as follows: from ground by way of the grounded release trunk conductor 20, normally closed contacts controlled by armature G3, armature 74 and its resting Contact, armature'and its working Contact, interruptor contacts il-2` of rotary.4 magnet 41, and thence to battery through .oft normal contacts and stepping gizes at-the end of the vertical ,movement, it opens the initial circuit of stepping relay 34 and complet-esa circuit for rotary magnet 41 as follows: lfrom ground by way` of the grounded release trunk `conductor 20, armature G2 and its resting contact, normally closedcontacts controlled by armature* 56, armature 5S Iand its working contact, and rotary magnet41 `to battery. yResponsive to the closure of this circuit, rotary magnet 41 energizes and advances the wipers 79,-31,.in-`

elusive,f into engagement with the iirst set of bank contacts in the selected level and, near the Lend of its stroke, opens at intern rupter contacts 42 the locking circuit of step ping relay 34. Then this occurs, stepping relay A34 deencrgizesand opens the circuit ot' rotary magnet 41 at Varmature 58, resulting in the deenergization of rotary magnet4l. In casethe trunk line connected with thc first set of bankcontacts is idle,' switching relay39 energizes immediately and seizesy the trunk. Assuming the trunk to be busy, howevenfswitehing relay 39 is short circuited `by the ground potential encountered upon the .busy test contact by test wiper and does not energize, and stepping relay `34 is` again energized through interrupter contacts 42 and oft normal contacts 45 and again closes its locking circuit atarmature. 57, and the circuit ot' rotary magnet 41 at ar mature 58, whereupon rotary magnet4l again energzcs and; advances the wipers into engagement with thenext set of bank contacts.

This alternate operation` ol` stopping relay 34 and rotary magnet 41 continues until an,

idle trunk is; reached, which trunk, it will be assumed, is the one comprising conductors S5 and 80 and exteinling to the icoming selector repeater E, Fig. iVhen uthis idle trunk is reached,` switching relay 39, being no longer short circuited, energims from ground on the grounded release tanni; com ductor 20 and in seriesawith steppingrelay 34 (stepping relay `34 not energizing atthis. time on account or' the high. resistance of switching relay 39)` and opensithe testccircuit and placesground on the test wiper ,S0 at armature73; removes stepping relay 34. from under thecontrol of relay at arma-V ture 7 6,' disconnects vertical magnet 42 from in multiple with the slow acting relay 33` at armature 7 5; disconnects ground from armature `57 of stepping relay 34 and preparesa circuit for relay 35 at varmature 74; dis.-` connects the dial tone machine lirourthc lower talking conductor at armature 78; and at armatures 72 and 77 connects the wipers 7 9 and Sl'to the bridge including the upper winding ot relay 37, andv disconnects the said bridge from battery and `ground locally. Relay 37 is now maintained `energized in series with line relay 101 of the in-` coming selector repeater E, Fig. 2,which iscouuected `to conductor S5 through the normally,closed contactsl controlled b.yarma-` ture 143, and through the upper left` hand repeating coil winding, conductor 3Gbeing grounded through thelower left hand repeating coil winding, the normallyy closed contacts controlled by armature 134, and the normally closed contacts controlledqby armature 142. Since relay 37 is maintained energized in series with the line relay oi` the switch E, it maintains the `circuit of relay 38 closed at armature 68, which relay in turn maintains the circuit of the switclrover relay 35 open at armature 70, which is the last remaining open point in theicircuit of the said relay 35.

In theincoming selector repeaterE, Fig.' 2, line relay 101, energizes responsive to, the,y above mentioned closure of" its circuit yand closes at armature 125 a circuit for release relay 102. y Release.k relay '102, upon` energiz4 ing, places ground onloclring conductor 118` at'armature 127 and at armature `12S pre.

`parcs circuit 'tor `vertical magnet` 117.@ As a further result or the energlzation Ofiline sok i gizing, opens at armature`139 `a point in the circuit oit switch-over relay 110,7so as to prevent the premature operation of the said relay.

Whe'nvthe calling subscriber manipulates his calling device in accordance with the second digit in the desired number, theini terruptions produced by his calling device are repeated at armature 51- by line relay 31, Whichhalso closes a circuit for relay 33 at armature 52. Relay accordingly energizes and, being slow acting, maintains its armature attracted throughout the series of interruptions.` Upon energizing, relay 33 closes a multiple circuit for relay 38 at the normally open contacts controlled by armature 56 in order to maintain relay 33 energized independent of armature (38 of relay 37, Whose circuit, as abovev pointed out, is opened at armature 51. ltwill be understood that relay`33 is able'to attract its armature a'nd closes the circuit ot relay 38 be fore relay `37 can retract its armature 63 and open'il the circuit of relay 33, owing to the fact 1that a `relay that is not stifl'ly adjusted is Mable to energize and attract its armature iin a shorter time than is required for arsimilarly adjusted relay to deenergize and retract its armature. Accordingly, re-y lay 38 remains energized during the series ofinterruptions and, at the 'end of the lastV interruption, its circuitis again closed at armaturei68` of relay 37 before its circuit is opened at-th'e normally open contacts .controlled by `armature 56 otrelay This operation, it will be understood, is repeated for each of the `remaining digits.

In the rincoming switch E, line relay 101 deenergizes in response to'each of the above interruptions and closes at armature 125 a circuit" for vertical magnet 117 through armature `123 and its Working contact and armature 151 and its resting contact. By the operation of vertical magnet 117, the

Wipers 153-155, inclusive, are raised stepv by step in the usual manner and cornes to rest opposite the desired level of bank conf tacts." Slow 'acting relay 103 is energized in 'multiple` with vertical magnet 117 an'd closes at `armature 129 a circuit for stepping relay 104, which circuit includes armature 149 and its resting contact and the off noi1-` malcontacts 113 which are closed` upon the lirst vertical step.` Stepping relay 104, upon energizing, `prepares a circuit -tor vertical magnet 115 at armature 130, and at' armature 131 closesa locking circuit for itself as follows: from ground by Way of the grounded locking conductor 118, normally closed contacts controlled by armature 145` of relay 110, armature 150 and its resting contact, Working contact and varmature 131, interrupter contacts 116, and thence to b`at-` tery by Way ot' oli normal `contacts 113and stepping relay 104.

When slow acting relay 103 deenergizes at the end ot the vertical movement, it opens they initial circuit of stepping relay 104 ati armature 129, and 'at the norm-.illy closed contacts controlled byl the said armature 129 completes a circuit :tor rotary magnet- 115. Rotary `magnet 115 now energizes` and rotates the Wipers 153-155, inclusive, intoengagement with thelirstiset of bank contacts in the selected level, 'after Which the operations 'are as described hereinbei'ore in connection With the lirst selector repeater D, until an-idle trunk is selected, Which trunk, it Will be assumed, istlie trunk comprising conductors 1131-163, inclusive,`

and extending to the thousands selector F,

Fig. 3. When this idlev trunk is reached,`

switching relay 111 energizes in series With the stepping relay 104 (stepping relay 104 not cnergizing'on account oi the high resist* ance oit switching relay 111) and opens the test circuit and grounds the test Wiper 154 at armature 143; disconnects vertical magnet 117 at armature 151; removes steppingrelay 104 from under the control of slow acting' relay 103 at armature 149; disconnects the grounded locking conductor 113` from arma ture 131 ot relay 104 and closes a circuit for relay 109 through armature 139 at` armature 150, leaving the circuit of the change-over relay open onlyat` armature 139 of relay 108. Relay 109 noW energizes preparatory to giving momentary assistance during the switch-over operation which is to taire place subsequently. At armatures 147 and 152 relay 111 connects the Wipers 153 and 155 to the bridge which includes the lower Winding of relay 105, and at the same time disconnects the local battery and ground conneci ions from the said bridge. Relay 105 is ncrv maintained `energized in series with line relay 201 of the selector F, Fig'. 3, which line relay 201 accordingly energizes `and closes at armature 221 a circuit through the resistance 212 andthe lower contact and oil normal spring 211 tor the combined release and change-over'relay 202. Relay 202, upon energizing, closes a point in the circuit of stepping relay 203 at armature 222, Which' circuit is still maintained open at oil normal contacts 210; opens at armature apoint in the circuit ot release magnet 205 andpres pares a circuit for vertical magnet 207; and at armature 213 connects the grounded `release trunk conductor 162 to armature 221', and disconnects direct ground therefromat the normally closed contacts controlled by armature 213. This is done so as to enable the selector F to be released in a mannerto bepointed out hereinatter in case the calling slubscriber hangs up wit-hout dialling another c igit. f y y Vhen thelcalling subscriber manipulates his calling ,device in accordance with the third digit in the desired number, the interruptions produced by his calling Adevice are repeated in the manner described hereinbefore at armature 51 byline relay 31 of the rst selector repeater D and the repeated interruptions are repeated in the same manner at armature 126 by line relay 101 of the incoming selector repeator E, Fig. 2.` Line relay 101 also closes atarmature'125 a circuit for the slow acting relay 103, whichis accordingly maintained energized throughout `the series of interruptions and maintains the circuit of relay 108 closed atthe normally open contacts controlled by armature 129 independe-nt of armature 133 of relay 103, which relay deenergizes responsive to the interruptions in the control circuit at armature 126.

1n the selector F, Fig. 3, line relay 201 is deenergized once momentarily each time its circuit is interrupted by the line relay of the switch E` and, upon each deenergization, closes a circuit for vertical magnet 207 as follows: i from i ground by way of the grounded release trunk conductor162, (which is maintained groundedthrough wiper 154 y of the switch E) armature 213 and its work` ing contact, resting contact and armature 228, armature 221 andV its resting contact, armature 223 and its working` contact, and vertical magnet 207 to battery. By the operation of vertical magnet 207, the` wipers 230-232, inclusive, are raised step by step and come to rest opposite the desired level ot: bank contacts. Upon the first vertical step of the switch, oft normal contacts 210 complete a circuit `for stepping relay 203 as follows: :from ground by way of the grounded release trunk conductor 162, which conductor is maintained grounded bythe incoming selector repeater E, Fig. 2, working contact and armature 222, oil normal contacts 210,` and stepping relay 203 to battery. Stepping relay 203 thereupon energizes and prepares a circuit for rotary magnet 208 at armature 2211. and at armature 225 closes a locking circuit for itself. This locking circuit includes the resting contact and armature 228, as well as the interrupter contacts 209, in addition to the oli" normal contacts 207 upon each deenergization of lline relay 201, and the slow acting relay 202 is maintained energized until the end ol the vertical movement, at which time it falls back responsive to the prolonged opening of its circuit by the line relay. Upon deenergizing, relay 202 disconnects the resting'contact of the i now operated armature 221 from the vertical magnet 207 and from its own winding, and prepares a circuit for the release magnet 205 at armature 223; replaces ground locally on armature 221` ot' line relay 201 and disconnects release trunk conductor 162 therefrom at armature 213; and opens at armature 222 the initial circuit of stepping relay 203 and completes the circuit of rotary magnet 208 through armature 224L and its working contact. Rotary magnet 208 thereupon energizes i and advances the wipers 230-232, inclusive, into engagement with the lirst set of bank contacts in the selected'level y -A and, near the end otits stroke, opens the locking circuit rof stepping relay 20,3 at interrupter contacts 209, whereuponstepping relay 203 deenergizes and opens the circuit ot rotary magnet 208 atarmature 224, resulting in the deenergization of rotary magnet 208, which again closes `its interrupter` contacts 209.

In case the trunk terminating in the first set of contacts is idle, switching relay 204; energizes immediately in series `with stepping relay 203 and seizes the trunk. Assuming the trunk to be busy, however, switching relay 2011 is short circuited by the ground p0- tential encountered upon `thebusy test contact by test wiper 231,` and stepping relay 203 is energized again, with the result that the circuit ot rotary magnet 208 is again closed at armature 224C andthe wipers rare advanced into engagement with the next set ot' bank contacts. This alternate operation ot' stepping relay 203 and rotary magnet 208 continues, as described, until an idle trunk is, reached, lwhich trunk, it will be assumed, is the one comprising conductors 233-235, inclusive, and extending to the hundreds selector G. r l y lVhen this idle trunk is reached, switching relay 201, being no longer short circuited, energizes in series with stepping relay 203, the said stepping relay 203 not energizing onaccount ot' the high resistance of switching relay 20%; disconnects ground from armature 221 of line relay 201 at armature 228, so as to prevent the energization of release magnet 205 upon the deenergization of line relay 201, whiclicoccurs subsequently;` disconnects test wiper231 `trom the junction of its own windingand that of steppingrelay 203 and connects it tov the grounded release trunk conductor 162 at armature 227, thereby grounding release trunk conductor 234 of the seized switch; and at armatures 226` and 229, connects thewipers 230 and 232 to the incoming t-runk conductors 161.and 163 and disconnects line relay 201 from the latter, whereupon line relay 20]: deeiiig'i'zes and closes apo'int inthe circuit oit release magnet at'arinature 221.

ln the `seized selector G, line relay 251 and relay now energizes and perform `the function which is `described for the` relays vnector H; vWhen this idle trunli is reached,

s"v'vitchinglt relay 253 of the selector G energizes` and seizes the said' trunk, whereupon ground is extended to the release trunk conductor2d2 and the incoming trunk conductors 233 and 235 are extended to the trunk conductors 241. and 2421i of the coni `nelcto'r H,fand line relay 251 is cut oli.

In the connector H, line relay 301, which is bridged across conductors 241 and 248 atof normal contacts 30T andBOS, now energizes y`an`d"`closes a circuit for release relay i302 asY follows: from ground by Way of the normally closed contacts controlled by ar'mature 323 ,oli Vrelease relay 302, armature 3^39`and its resting contact, armature 3,31 and its" resting Contact, armature 232i and itsWorking'contacu and release `relay 302 to battery. Release relay 302, upon energizing, closes a locking circuit for itself at armature 324; which isindependent of armature 321. and its Working Contact; shifts its initial circuitat `armature 323 from ground locally to ground by "ay off thegrounded release triinlrv conductor 243; opens a point in the circuit of releaselmagnet 3l() at armature SQJiandprepare/s the operating circuit; and at armatures 322 and 326 shunts the oli7 normallcontact's 307and` 308, respectively, so as'to maintain the line rela-y 201 bridged across the trunk conductors 2li and 243 after these olf normal contacts have been `o'lened upon the rst vertical step ot the pletes a circuit for vertical. magnet 3l?,

meegaat which entends from ground as previously traced tofarinature 321, and thence by Way ofthe resting contact ot' the said armature, armature-825 and its Working contact, armature 328 and its'worli'ing contact, and vertical magnetBlB to battery. By the opera-` tion ot' vertical magnet 313, the wipers Blildl, inclusive, are raised step by step and come to rest `opposite the desired level oi bank contacts. Uponthe iirst vertical step, oilnormal contacts Y307 and 50S open, leavingline relay' 301 bridged across the line only through armature 322 and its Working contactnnd armature 320 and its Working contact of relay 302. Slow acting relay 305`is energized( in multiple with vertical magnet 313 and at armature extends ground from the grounded release ltrunk conductor 242 through armature 350 and its vvorling contact, to relay 303 before the initial circuit of relay 303 is opened at olil normal contacts B00 upon the lirst vertical step. Y

At the end oi. the vertical movement slovv acting relay 305 deenergizes and opens the circuit of relay 303 at arn'iature 33d, whereupon relay 303 deenergizes and opens its locking circuit at armature 2350, and at armature 328 disconnects vertical magnet l'and connects up rotary magnet 312.

lVhcn the calling subscriber manipulates his calling device inaccordance f'ith the next and iiiial digit inl the desired number, line relay 301V is deenergiZed a corresponding number of times and, upon each deenergization, completes the circuit o'l rotary magnet 312, whereupon the wipers l-lil-li, inclusive, are rotatedinto engagement with the bank contacts'in Wliichvthe line oi.: substation A' terminates. Slow acting rela-y 305 again maintained energized during the series oit deenergizations oi" line relay :501 and at arniatureS-'SB disconnects test wiper H2 :from the upper Winding of switching relay 500 and connects it instead `to busy relay 304. Relay 305 also places a shunt around armature 331 and' its resting contact at armature 3235, so as to prevent the premature opening of the circuit oit release relay 802 in case busy relay Sil-l energizes due to test Wiper Mo Orl.' the rotary movement.

Assuming the called line lo be busy, busy relay 30d is energized when test wiper 342 arrives at the test Contact of the called line, and preparesa locking circuit ior itself at armature 330 and at armature 331, opensA a point in the circuit oi' release relay 302, While at armature 332 it prepares the busy signalling circuit. Accordingly, when relay 505 falls back at the end of the rotary movement, busy relay 30d becomes locked to the grounded release trunk conductor B43 through the normally closed contacts controlled by armature 337, its own armature passing over busy test contacts during lua `switches involved in the attempted connection, are released in a manner to` be ex-` L plained more in detail hereinafter.

It'vvill. now be assumed that, when the subscriber at substation A is called .by the subscriber at substation A in the hereinbefore described manner, the `line of substa-` tion Af is ldle.`

"lhat being the case, no circuit is closed for busy relay 304 when the wipers 341-343,`inclusive, arrive upon the bank vcontacts of the called line and, when relay 305 deenergizes it disconnects busy relay 304 at armature 333 and completes a circuit for the upper winding of switching relay 306 as follows: from ground by way of the grounded release trunk conductor 242, normally closed contacts controlled by armature 337, armature 330 and its working contact, upper winding ot' switching relay 306, resting contact and armature 333, wiper 342, private'normal conductor 345, switching 'relay 347 of the called line switch C, and stepping magnet 349 to battery. Switching relay 347 energizes over this circuit, but stepping magnet 349 does not energize on account of the high resistance of switching relay 347.` Relay 347, however, pulls up onlyhalf way onaccount of the usual interlocking device (not shown) between its armature proper and that ot' linerelay `348. Accordingly, the bridge across the line conductors is removed but the associated wipers are not connected up. l,

In the connector H, switching relay G energizes in series with-relay 347 over the above traced circuit, but due to the Jactwthat ithas `a copper slugon itsarmature end, as denoted by the black ,upper portion of the core,=it is slightly slow in pulling upso as to" give plenty of time for the energization of relay 347, to become effective before the line wipers are connected up. Upon pulling up, relay 306 closes a locking circuit for itself at its light-ly adjusted armature 333 connects the grounded release trunk conductor 242to test wiper 342 at armature 337, at the same time disconnecting armature 330 `of busy relay 304 from the said release trunk conductor 242 so as to prevent the upper winding of switching relay 30'6rom being sort circuited and having a retarding effect upon "the rrelease of the relay when the circuit of the lower -winding` is `subsequently opened ;V and,` at armatures 336 and 340 connects up the line wipers 341 and 343, respectively, whereupon ringing current is intermittently projected out over the called line to ring the bridged bell at the substation A.

As a further result of the energization of switching relay 306, it brings about the switch-over operation in a manner to be pointed out, resulting in the circuits in the switches D and E being shifted from dialling position into position to await the an-` Specifi-` cally relay 306 opens the circuit of release relay 302 and prepares a lockingcircuit foriy ring cut-of relay303 at armature 339` Re swering of the called subscriber.

lay 302` thereupon deenergizes; disconnects line relay 301 at armatures 332 and 326, allowing it to fall back; prepares the release magnet circuit at armature 325i; opens a point in its previously established locking circuit at armature 324; and` at Aarmature 323 disconnects the groundedrelease trunk conductor 342 from armature 339 and replaces local ground on thesaid armature `so as to provide a circuit for subsequently energizing release magnet 310. p

In the incoming selector repeater E, Fig. 2, relay 105 deenergizes responsive to line relay 301 being disconnected in the connector H, as pointed out above, and opens the circuit of relay 10S at ary-mature 133, whereupon relay 108 deenergizes and opens at armature 139 the circuit of relay 109 and conipletes a circuit for switch-overrelay 110. Relay 109, however, being slow acting, does not deenergize immediately. The circuit of relay 110 `which is closed at armature 139 is as follows: `from ground byway of the grounded locking ,conductor 118, normally closed contacts controlled by armature 145, armature 150 and its working contact, armature 139 and its restingcontacuand switchover relay 110 to battery. Relay 110 thereupon energizes and closes a locking circuit :for inself at armature 145; opens a further point in the circuit of slowacting `relay 100 at well as its own initial circuit at the normally closed contacts controlled by armature 145; prepares a holdingcircuit for line relay 101 at the normally open contacts controlled by armature 145; removes relay 108 from under the control of relay 105 at armature 144; completes a local circuit'lor line relay 101 through armature 140 and its working contact at arnulture 142` at the same time removing ground from the lower left hand repeating coil winding and consequently from the lower trunk conductor S6; and at armature 143 bridges the high resistance relay 107 across the condenser inserted between the left hand windingsof the repeating coil; and disconncctsline relay 101 from the upper left hand repeating coil winding at the normally closed contacts controlled by the said armature 143, thereby completely substituting the high resistance bridge `inf` cluding relay 107 for the battery and ground connections across conductors and 86.

At armature141` relay 110 disconnects the bridge including the `lower winding of relay 105 front-across thewipers 153 and 155, and atarrnatures 1&1 and 1;16 connects the wipers 153 and 155 to battery and ground, respeo tively, through the upper and lower repeating coil windings, wiper 151 being connected i bridge is closed across the line wipers preparatoryito feeding talking battery to the called substation when the subscriber thereat responds i and,l since it is desired to subsoquently place the continuity of this bridge under the `control of supervisory relay 107 after the switch-over operation in the` first selector repeater has been completed, the bridge is closed as above pointed out through armature 1111 and its working contact ot the slowacting relay 109, `which will tall bach subsequentlyv and leaye relay 107 to control the bridge at armature 130 as will hereinafter appear.

In thefirst selector repeater D, Fig. 1, relay 37 ideenergizesin response to the removal of the current source from the bridge across conductors 85 and 80 in the incomingl selectorlE, Fig. 2, as described above and opens the circuit of relayBS at armature 5&3, whereupon relay 38 deenergizes and closes la circuit for relay 35 as follows: from ground by-fway` of the grounded release trunk conductor 20, normally closed contacts controlled by armature 63, armature 74 and its working contact, arinature 70 and its rest ing contact, and relay 35' tobattery. Relay 35 thereupon energizes; closes a locking circuit 'for itself and opens the initial. circuit at armature 03,211'. the saine time preparing a locking circuit for relay 3S; disconnects ground 'from the working contact of arnia4 ture 5610i relay 33 at armature 62, so as to render any subsequent `energiaation of re lay 33 ineifeetive in operating relay 38; at arniatureGQ and its working contact prepares `a circuit for grounding the meter operating*conductor 19 upon the nent enorgizaf tion of relay ,38; con'ipletes .the inductive connection between the calling line and the switch wipers through the talking cmidens at armatures 01 and 00; at arnuiture tiel disconnectsthe upper windingo'l1 relay 37 from across the line wipers 79 and 8l; and at arinaturesl and bridges the dillerential relay 36 and the battery feed relay 37 in series across the line wipers 79 and 81, ground being extended to wiper 81 through the lower winding of the differential relay 86, worlringcontact and armature 65, upper winding of relay 37, and the working contact and armature 7 7, and battery being ero tended to wiper 79 through the lower winding of the battery ieed relay 37, upper winding of the differential relay 36, worlringcontact and armature 04:, working Contact and armature 51, and the working contact and armature 7 ln the incoming selector repeater E, Fifa 2, the high resistance relay 107, which'is' because its windings are dillerentially con-j nected at this tinieand relay 37 does not energize on account ot the high resistance ot relay 107 in the incoming selector repeater E.

Relay 107. upon energizing, closes the'ifol lowing circuit for relay 101 before relay 109, which is now holding relay 101 energized at armature 1110, has had tiine'to deenergize:

troni ground by way oli' theA grounded lock: ing conductor 118, normally open contacts controlled by armature 145 of switch-over relay 110, armature 137 of relay 107 and its working contact, and relay 101 to battery. 11s a further result of the energization'of relay 107, it shunts armature 1111 ofrelay 109 at armature 130 so as to hold the battery feed bridge closed after relay 109 has fallen back.

The circuits are now in readiness for th answering supervisionto be relayed back to operate the meter M when the called man answers. y

When the subscriber at substation A responds to the ringing of his bell by removing hisv receiver, the direct current bridge including his receiver and transmitter is substituted for the ringer bridge including the condenser, whereupon ring cut-oil relay 3023 of the connector H responds;closes alocking circuit for itself at armature 350,A which circuit includes the normally closed contacts controlled by armature 323 of relay 302'and armature 339 and its working contact; and at armatures 327 and 329 disconnects the line wipers 341 and 8113 from its own winding and ground and connects thein instead to the conductors 2&1 and 243, thereby tinallyA completing the talking circuit. Talking battery is now supplied to the called substation A through the upper and lower windings of the differential relay .100 inthe incoming selectori'epeater E, Fig. 2, the upper winding of supervisory relay 105and the right hand repeating coil windings. Accordingly, supervisory relay 105 becomes energized and attracts its armatures 132 and Relay 106, however, is not energized loo lili

lll)

wound.` Accordingly, relay Sfupon energizing, completes at urniature` G8 a circuit.

for relay 38 which includes armature 6T and its resting contact. Relay `88, upon energizing at thistime, closes a locking circuit for itself at armature 71 as follows: from ground by way of the grounded release trunk conductor 20, normally open contacts controlled by armature G8 of switchaiver relay 35, armature 71 and its working contactfand relay 38 to battery. -Relay 38 also closes at armature 69 a circuit for the meter M as follows: from ground by way of the grounded release trunk conductor 20, armature 62 and 'its workingcontact, working contact and armature G9, the meter operating conductor 19, contact in the bank el wiper 15 and said wiper, working contact and armature 9, andthe magnet of the meter M :to battery. Upon energizing, the magnet ture 68.

of the meter M advances the associated number wheels to register the successful calll Since relay 38 is now locked energized at armature 71 independent of relay 87, as above pointed out, the magnet of the meter M remains energized untilthc connection is released regardless of any .operations of the called subscribers switch-hook.

`When the conversation is terminated, the subscribers at substations A and 'A' replace their receivers. i Assuming` that the receiver at substation A is replaced first, supervisory relay 105 in the incoming `selector repeater E deenergizes responsive to the called subscribers receiver being replaced and at armature 1232 removes the shunt 'troni around the upper winding of the hi gli resistancerelay 107, whereupon relay 3T inthe first selector repeater D deenergizes and opensthe initial circuit of relay 38 at arma- Relay 38, however, does not deenergize owing to its previously traced locking circuit. i

When the receiver is replaced at substation A, line relaylof the first selector repeater D deenergizesandopens at armature 52 the circuit of release relay and` at armature 51 opens the bridge across wipers 79 and 81. Release relay32, being-slow acting, does not fall back for an interval. ltelay 107, however, ot the incoming `selector repeater E, Fig. 2, immediately decnergizes responsive to the release of armature 521 or' line relay 31 of the switch D; opens at armature 13G the battery feed bridge across the wipers 153 and 155 and opens at armature 187 the circuit o;t` line relay 101, whereupon linev relay 101 deenergizes also and opens at armature 125 the circuit of release relay 102 and closes a circuit Jfor 4relay-103 through armature 128 and its working contact. Relay 103now energizes `and closes a circuit for relay 108 at the normally open contacts controlled by armature 129, whereupon relay 108 energizes and attempts to close a circuit for relay 109 at armature 189. This circuit, however, is now open at contacts controlled by armature 145.

In the first selector repeater D, Fig. 1, release'relay 82 deenergizes after the interval for which it is adjusted and removes ground from release trunk conductor 20 at armature 32,*at the same time opening the circuit of theslow acting relay 33 (which energized responsive `to the deenergization of 'linerelay 31) and closing a circuit for release, magnet 40 at armature 5st. Responsive to the rcmoval of ground from release trunk conductor 20, switchover relay 35,`switching relay 89, and the meter operating relay 38 de energize. The deenergization offrelays 35 and 39 does not have any `particular function at` this time except to restore the circuits controlled thereby to normal, and the deener` gization of relay 38 results merely in the opening ol.z the circuit `of the magnet of the meter M, whereupon the said magnet deenergiz'es. Responsive tothe closure of its circuit at armature 54, release magnet A40 energizes through oli normal cont-acts 44, whereupon the wipers 79-81, inclu'sive,"of the selector D are restored tonormal position in the usual manner and the circuit of release magneti 410 is thereupon opened at olf normal contacts 111. i l

As a further result of the removal of ground potential from release trunk conductor 20, the busy potential is removed from private normal conductor 4 of the calling line and switching relay 5 of the line switch C deenergizes. l

In the incoming selector repeater E, Fig. 2, upon the deenergization of release relay 102 at the end ot the interval for which it is adjusted, ground is removed from conductor 118, at armature 127, whereupon relays 108, 110, and 111 deenergize. As a further result oit the deenergization of release relay 102, it opens the circuit of slow acting relay 10B andeompletes a circuit for release magnet 11S?l at armature 128, resulting in the subsequent deenergization of relay 103. R`esponsive to the energizationl of `release magnet 112, the wipers of the switch are restored to normal position in the 'usual manner, whereupon the circuit of release `magnet 112 is opened at ott normal contacts 114.

As a 'Further result of the above mentioned deenergization of release relay 102 of the in-" coming `selector repeater E, ground is removed from the private Wiper 154; which results in the holding ground tor the switches F, Gyand H being removed. lhen this occurs, switching `relay 20st in the selector F, switching relay 253 in the selector G, and switching relay 806 in the connector H deenergize. The deenergization ot switching relay 204 of the selector F results in a circuit being closed for 'release magnet 205 as fob lows: from ground by Way ot the normally closed contacts controlled by armature 213, resting contact and armature 228, armature 221 and its resting contact, armature 228 and its resting contact,1otf normal contacts 206, and release magnet 205 to battery. Upon the energizationot release magnet 205, the Wipers ot the selector FI are restored to normal position in the usual manner. The selector G is restored to normal position in the same manner as the selector F.

In theconnector H, release relay 30G, upon deenergizing, opens the locking circuit ot relay 303 at armature `339, resulting in the deenergizationof relay 303, and at armature 389 and its resting contact closes a circuit .tor

release magnet 310 as` follows: from ground i by Way of the normally closed contacts controlled by armature 323 of rela-y 802, arma ture f389.]and its resting contact, armature 331 and its restingcontact, armature 321 and its resting contact, armature 825 and its resting contact, oft` normal conta-cts 311, and release magnet 310 to battery. Release mag net 310 non7 energizes and the wipers ot the switch are restored to normal position in the usual manner.

The entire connectionis now released and the switches `involved are in readiness to be used `in `a subsequent connection. It will now be' assumed that the subscriber at substation-A` desires to converse with the subscriber at substation A3, Fig. `9, Whose line terminates in an otice which has not yetbeen converted; to automatic operation. That being the case, the connection must be coin` pleted by a B operator inthe manual oltice, Whose position is indicated in Fig. 0. Accordingly, the subscriber at` substation A removeshis receiver and dials the necessary digits to trunk the call to the desired manual oiiice. In this case 4it has been assumed that the desired manual office is in the saine district as the automatic office in Which the line of substation A, Fig. 4, terminates. Acn cordingly, the incoming` selector repeater E, Fig. 2, Whose function from a trunking standpoint 4is that of an office selector, may be used to complete the `connection to the operators position after it has been seized by a district selector, such as the firstselector repeater D, Fig. 1.

When the receiver is removed at substation A, the line switch C operates in the :hereinbeforedescribed manner to select an memos idle trunk, which trunk, it will be assumed, is the one extending tothe first selector rcpeater D. Accordingly, the line and release relays 31 and 32 of the irst selector repeater D energize following the energization of the switching relay 5 oit the line switch C and perform the ituiictions pointed out hereinbe'tore.

When the calling subscriber operates his calling device in accordance with the tlrst digit, the switch D raises its Wipers in the hereinbefore described manner and selects an idle trunk, which will be assumed `to be the trunk Comprising conductors and 8G and eI-:tending to the incoming selector repeater E, Fig. 2. Accordingly, the `line and release relays 101 and 102 of the incoming selector repeater E energizes With the liereinbefore pointed out results.

When the calling subscriber manipulates his calling device in accordance with the second `and last digit necessary to extend the connection to the B position shown in Fig. 9, the selector E raises its Wipers opposite the desired level of contacts and selects an idle trunk in the hereinbetore described manner, which trunk, it Will be assumed, is the one comprising conductors 164 and 165 and extending to the plug ending cord circuit, shown in Fig. 9. That being the case, the energization ot switching relays 111 of the selector E results in the extension of the callingloop to conduc tors 164 and 165. In this case, no battery feed is found `to maintain relay 105 encrgized after the battery through resistance 119 has been `disconnected at the normally closed contacts controlled by armature 147, and relay 105 deenergizes, opening the circuit ot relay 108 at armature 133. Relay 108 accordingly deenergizes and completes the circuit of the switch-over relay 110 at armature 139, whereupon switch-over relay 110 energizes and connects up the back bridge circuit .at armatures 141 and 141-6, and i at armatures'142 and 143 substitutes the front bridge supervisory relay 107 for the line relay 101, whereupon the switch-over operation in the first selector D takes place as hereinbeforc described.

At `the B operators position. Fig. 0, relay 801 now energizes responsive to the above mentioned switch-over operation in the incoming `selector' repeater E, Fig` 2, and closes :a circuit for the supervisory lamp 808 at armature 807, which circuit includes armatures 810 and 811. The lamp 808 thereupon becomes light-ed to `inform the B operator of the call.

lVhen the operator responds by throwing her combined listening and ringing key K3 into listening position, thereby connecting up her listening taps, the said key closes a circuit forrelay 802 which energizes and locks itself` up through armature 806 and lun its Working Contact at armature 809.` "Relay 802 also extinguishes the lamp `808 at armature 810.

The B operator now converses with the calling subscriber and, upon learning his desire, inserts the plug of her cord circuitinto the jack J2, resulting in the energiza! tion ot sleeve relay 803 in series with the eutsotll relay of the called line, which cutoff relayenergizes and removes the normal' calling bridge. Relay S03, upon energiz` called subscriber responds, the supervisoryk relay S04 energizesand shunts the high resistance Winding of `relay 801 at armature 805, whereupon relay 105 in the incoming selector repeater E responds and short circuits the high resistance winding of relay 107 at armature 132. When `this occurs, relav 37 in the first selector repeater D encrgizes and closes a circuit for the meter opeating relay 38 at armature `(3S, whereupon relay 38 energizes and completes the hereinbet'ore traced circuit for the magnet of the meter M at armature 69.

The calling and called subscribers may now converse with each other desired and when the conversation is terminated they replace their receivers.

Then the receiver is replaced at substation A", supervisory relay 804 deenergizes and removes the shunt from around the high resistance winding of relay 801, Whereupon relay 105 of the incoming selector repeater E, Fig. 2, deenergizes and removes the shunt trom around the high resistance Winding ot relay 107 resulting inthe deenergization of relay 37 of the first selector repeater D, Fig. 1.

`lVhen the receiver is `repla'ed at substation A. the first selector repeater D and the` incoming' selector repeater 1G release in the hereinbefore described manner.`

Responsive to the bridge across the con ductors 164 and 165 being removed by the incoming Vselector repeater E, relay S01 in` the B operatoi"scord circuit, Fig. A0, dc-

energizes and completes at armature S07 a' disconnects circuit foi-the lamp 808 through the Working Contact of armature S11 and said armature of` the sleeve relay 803. Upon observing the lighted condition 'ot'the lamp 808, the B operator pulls down the coni nection, whereupon sleeve relay 803 dcenergizes and extinguishes the lamp 808.,and the cut-ofil relay of the called line deenergizes also.

In order to be able to point out clearly certain features of the present invention v pertaining to the holding ot the connection by anoperator, it Will be assumed that the subscriber` at substation A desires to make a toll call and must therefore first get into communication with the toll recording oper-l ator, who will sce that the `desired toll connection is set up. The toll recording operators position is indicated in Fig. 8 and may be reached by the subscriber at sub-4 station A through the medium :of a` first selector repeater, such as the sivitch D, Fig. 1, and an incoming selector repeater, such as thesivitch E, Fig. i i i It will be assumed that `\vl1en' thesubscriber removes his receiver, the .line switch C selects the selector D; `andthat, when .theV calling subscriber `manipulates his c calling device for the first digit, the selector D selects the trunk extending to the selector Egand that, when the calling subscriber manipulates his calling device in accordingwith the second digit, the selector Eselects the trunk comprising` conductors 166 and 167 and extending to the trunk circuitat the toll recording operator-s position,` Fig. 8. Ac! cordingly, the switch-over operations inthe `tirst selector repeater D and the incoming selector E take place responsive to the seizure of the trunk leading to the toll recording operator-s position on account ot' the tact that no source of `current is bridged across conductors 166 and'167 to maintain relay 105 energized. 4As soon as the switch-over. operation in the incoming selector repeater 'E has taken place, battery is placed on Wiper 153 through the upper right hand repeating` coil winding, and ground is placed on Wiper` 155 through the lower right hand repeating coil winding, resulting. in the energization" of the high resistance line relay 702 `at the toll recording operators position,` Fig. 8." Relay 702, upon energizing, `closes at arma-` ture 705 a circuit through spring 709 of the answering key K for the answering lamp 711. which accordingly becomes lighted.

VWhen the toll recording operator notes: the lighted condition of thelamp 711, she operatesher answeringkey K', thereby erw` tinguishing the answering lamp 711 at the spring 709, and she also manipulates hei" listening key K2, thereby connecting` up he'r` listening taps to the `talking circuit.` The operator nowconverseswith the calling sub-`A scriber and makes the proper record of his \\'a1its,.after which she restores hor listening key K2, leaving the answering key 1K operated. Y

Vhen the calling subscriber.replaces his receiver, line relay 31 of thevseleetor D deenergi'zes and opensthe bridge across the line Wipers at armature 51 at the same time opening the Vcircuit .o't' release relay 32 at armature 52." Release relay 32. however, being slow acting, doesnot fallback; immediately. peater E,irelaysl07 reenergizesin response to the fenergizationof the linel relayof:

In the incoming selector re lill lll"

llt) 1 `at i armature `125.

`time to deenergize.

the "switch D .and opens the circuit of `:line relay 101l at armature 137, whereupon `line relay10.1#deenergizes and opens the circuit of the slow acting release relay .102 Relay 102, being slow acting', `remains operated lor the time Abeing. Relay 107, also opens the `l'iridge across the line `Wipers at armature 138, where upon 4line relay v702 at the toll recording operatorls position, Fig.` 3, deenergizes-:and closes a disconnect circuit for the lamp 711 at armature 705. Relay 702 also closes at armaturei704 a circuit forthe holdingrelay 701 through spring 7 (18ctV 'the key K- and `its associated contact. Relay 701, upon energizing, grounds locally the lower terminal of line relay 702 and rdisconnects it from the lower trunk conductor 167 at armature 707., and at armature 710 connects battery through resistance 706 to conductor 167. i

In the selector repeater E, the diillerential relay 1106 now energizes responsive to `battery being pla-ced on the lower talkingconductor at the toll operator-s position and closes at` armature 138 a circuit for line relay 101 which lincludes armature 142 and its Working contact. Line relay 101, upon energizing, closes at armatureill a circuit lior release lrelay 10i)J before the said relay has had Differential rela-y 106 also connects aground potential obtained from the grounded locking conductor 113 throng-lr the normallyl open contacts i oon-` trolled by armature 145 to vthe lower terminaflot' relay 107 and disconnects the `sai-d terminal` from conductor 86 at armature 134, and at iarniature 135 connects battery to conductor 86 through the lower left hand repeating :coilVwindin-g. In `the selector D., relay 37`and dilerential relay 36 now energizes `in series responsive to the battery being placed onlthe lower talking conductor, and relay 3'6clo`ses at `armature 67 a circuit for rel-ease relay 32 before the latter has had time to deencrg'ize. The energization `of relay 37 is merely incidental at this time.

In thefabove manner the entire connection 1s held up by the battery placed on the lower talking conductor `at thetoll recording op-` erators position, It will be appreciated `that the principal noveltyot this arrangement resides in the tact that a loop talking circuit is provided throughout `and that the talking circuit in any one case is normally grounded at one end only, and that the grounded holding battery is connected to the lower talking conductor to hold up the connection after the. calling subscriber has replaced his receiver and `is not connected to the talking circuit during conservation.

Assuming that the calling subscriber replaced yhis receiver' merely to attract the op erators 'attention because hedesires to con verse further, and that he again removes the lreceiver 'after a short interval, or `that the subscriber, instead -of actually replacing his receiver, merely moved thc switch-hooi; down and then let itup again, the disconnect lamp `711 at the operators position, l? 3. is again through the upper lett handrepeating coil winding' of the incoming' selector repeater' E, and through the working' contact andermature 143, and is grounded throughthe worlring vContact and armature 134, the normally open contacts controlled by armature 145, and the grounded release trunk conductor 118. Relay 107, upon energizing, places battery on the line wiper of the switch l at arnnrture 136 through vthe upper windings ot relays 105 and 106. "his results in the ene "gization of "line relay 702 at the operators `position, the lower terminal ol the said linie relay being grounded through armature 707 and its working contact. Upon energizing', line relay 702 extinguishes the lamp 711 at armature 705, and at armature 704 opens the circuit of relay 701. Relay 701 thereupon deenergizcs and restores the loop conditions to the trunl circuit, at the saine time removing battery and ground :from the said trunkcircuit. Relay 7 02 is now maintained energized over "the loop extending back` to the incoming selector repeater E, Fig. Q, and the differential relay 106 defener-gizes and retracts its armature 133, leaving the energization of line relay 101 under the control of relay 107, and res'storing the loop connections across the trunlr rizonductors 35 and 86 at the normally closed contacts controlled by armature 134, and removingl the ground and battery connect-ions at armatures 134 and 135. Consequently, the differential relay 36 and relay 37 in the lirst selec-- tor repeater D deenergize right away, and relay 36 opens the multiple circuit ot release relay 32 at armature 67, leaving relay 32 energized through armature 52 or line rclay 31. The circuit conditions are now the same as they were before the calling subscriber depressed lhis receiver hook, and the above operations may be repeated as many times as desired, in case he moves hisl receiver hook upand down several times solely to attract the attention ol the operator.

Assuming that `the calling subscriber has finished his conversation and does not remove hisreceiver after havingl replaced it With the above described results, the operator, upon noting the lighted condition ol' the lamp 711, restores her' answering hey ill 

